Flue coating is a process that involves the application of a protective coating to the interior walls of a chimney or flue. The coating helps to prevent the buildup of SOOT, which is a black or dark grey powdery or flaky substance made up of amorphous carbon particles. SOOT is created when fuel is burned incompletely and can cause blockages in the flue, leading to dangerous levels of carbon monoxide in the home. Flue coating helps to reduce the risk of this happening by providing a barrier between the fuel and the flue walls.